Patent Number: 6,166,501

Title: Index signal generating circuit

Abstract: An index signal generating circuit for generating a precise index signal free from time shifting even under ambient temperature changes. An index signal generating circuit includes a magnet attached onto the circumference of the rotor of a spindle motor, a magnetic flux detecting device for detecting magnetic flux of the magnet when the magnet moves past the magnetic flux detecting device, a Hall effect device for switching a current in the driving coil of the spindle motor, a first waveform shaping circuit for shaping the detected output of the magnetic flux detecting device into a rectangular-wave signal, a second waveform shaping circuit for shaping the output of the Hall effect device into a rectangular-wave signal, and a logic circuit for ANDing the output rectangular-wave signals from the first and second waveform shaping circuits, wherein an index signal is generated at the timing of a transition of the AND output of the logic circuit.

Inventors: Furuki; Shigeru (Fukushima-ken, JP), Sekine; Mikio (Fukushima-ken, JP)

Assignee: Alps Electric Co., Ltd.

International Classification: G11B 19/247 (20060101); G11B 19/24 (20060101); H02P 6/14 (20060101); H02P 6/16 (20060101); H02P 006/16 ()

Expiration Date: 12/26/2013